The subject invention is generally directed toward a biocidal composition of an organotin compound covalently bonded to a silica compound to control the activity of the organotin compound. Further, a method for protecting a surface from foulants is disclosed through the use of the subject biocidal composition.
The use of organotin compounds of the general formula: EQU R.sub.3 SnX
wherein R is a lower hydrocarbyl group and X is an anionic radical such as oxide, sulphide, halide and organic acid radicals have long been recognized in the art as being an excellent biocidal compound effective against marine growth. Generally organotin compounds are incorporated into a coating composition which can be applied to the hull of a ship or any other surface which will be in contact with the water. The coating then releases the biocidal compound into the water to prevent marine growth. Naturally as the biocidal compound diffuses to the coating's surface and is released the effectiveness of the biocidal activity will decrease with time. Therefore, one goal has been to control the rate of biocidal release to prolong the effective life of the coating composition.
One method directed toward the slow, steady release of the biocidal compounds is attempted in U.S. Pat. No. 4,115,130. There the particular biocidal compound is entrapped in the internal porous structure of silica. While this method is said to slow down the escape of biocidal compounds there still remains room for improvement.
Another method disclosed in U.S. Pat. No. 3,854,960 attempts to retain a triorganotin compound in paints by admixing it with colloidal silicic acid obtained by the flame hydrolysis of silicon tetrachloride, i.e., fumed silica, or montmorillonite modified with quaternary ammonium salts. The advantage is disclosed as being due to the presence of silicon or montmorillonite in the paint and less on an adsorptive binding of the tributyltinoxide.
Despite the many methods known it is still desirable to control the biological activity of organotin compounds to better utilize them as antifoulants. Further, it is desirable to have a compound which can be dispersed in a carrier or coating vehicle of choice without regard to further modification of the particular vehicle.